Centrifugal fan.



J. KEITH.

CENTRIFUGAL FAN.

APPLICATION FILED 0013.21, 1910.

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GBNTRIFUGAL FAN.

APPLIUATION FILED OCT. 21, 1910.

' Patented Jan. 16, 1912.

3 SHEETS-SHEET 2.

INVENTOR J. KEITH.

GENTRIFUGAL PAN.

APPLICATION FILED 01. 21, 1910.

Patented J an. 16, 1912.

3 SHEETS-SHEET 3.

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UNITED STATES PATENT OFFICE.

JAMES KEITH, OF 'LONDON, ENGLAND.

CENTRIFU'GAL FAN.

.London, England, have invented a certain new and useful Improvement inCentrifugal Fans, of which the following is a specification.

This invention contemplates certain improvements in centrifugal fans ofthe type described in the specification ofLetters Paten-t No. 935,114 of1908. In the said specification there is described a. fan runner hav inga number of tapered blades (32 or thereabout) of which the outer andinner longitudinal edges lie on substantially conical surfacesdifierently inclined to the axis of the fan spindle the inner cone beingof shallower dimensions than the outer cone, so that the diameter of therunner is greatest where the bladesQare narrowest. With this fan, as theperipheral speed is greatest toward the inletwhere the external diameteris greatestand the resistance offered by the blades is greatest at theback ends of the blades-where these are deepest-the tendency of theentering column of air to rush to the back of the fan, due to itsInomentum, is largely or wholly overcome, and the delivery of air issubstantially equalized over the length of the outer longitudinal edgesof the blades. In the fan described in the said specification I havedescribed the blades as being so disposed that their outer longitudinaledges are practically co-planar with the axis and theirinnerlongitudinaledges are inclined to a plane including the axis-that is, these edges ofthe blades are not only not parallel to each other but are not evenco-planar.

Further experiments made particularly with fans having relativelyshortblades have led me to devise certain arrangements which may beconsidered as modifications of that described in the said specification,the elliciency of those fans fluctuating more or less according to theconditions of speed, volume and pressure; but each construction (someforms of which are also-described and claimed in my co-pendingapplication, Serial Number 602,885, filed January 16, 1911) may beregarded as in itself meritorious and, within those limits where itsellicienry reaches a. maximun'i as possessing certain mlvaulugi-s evenvcr the original or standard Keith fan.

Specification of Letters Patent.

Pate nted Jan. 16,1912.

Application filed October 21, 1910. Serial No. 588.314.

other of a centrifugal fan of the open type. Figs. 3 and 4 are likeviews of a case fan having blades of, different form. Figs. 5 to 9 showmodified constructions of blades.

Thenew fan runner comprises as heretofore a number of tapered andscooped blades of which the outer and inner longitudinal edges lie onsubstantially conical surfaces differently inclined to the axis of thefan runner, the outer cone being less inclined than the inner cone, andboth cones being truncated, the narrow ends of the blades being held bya ring which constitutes the end ofthe runner of maximum diameter andthe deeper ends being fitted to a disk constituting that part of therunner of, least diameter.

In the open fan runner shown in Figs. 1 and 2, the blades are so setthat both the outer and inner longitudinal edges a and b, respectively,are oblique to a plane including the axis of the fan runner, the outerlongitudinal edge a of any given blade sloping rearw'ardly from animaginary plane including the axis and the inner longitudinal. edge I)sloping forwardly from the said plane, 2 e. in the opposite direction;that is, assuming that said plane be rotated around the axis of therunner, both longitudinal edges of each blade will deviate from the sameplane and in opposite direcof the blades slope forwardly in the direc-'tion of rotation and the inner longitudinal edges 6 slope rearwardlyfrom said plane.

In the construction shown in Fig. 5 the outer longitudinal edges a ofthe blades slope rearwardly and the inner longitudinal edges 1) slopeforwardly. It will be understood that in this case the runner is rotatedso that the concave surfaces of the plates are presented to the air.

I may so far vary these constructions as to decrease the obliquity ofthe inner longitudinal edges 6 so as to make them coplanar with theaxis, Figs. 6 and 7. Or. I may vary the form or curvature of the bladesso that the inner longitudinal edges Z) shall be oblique to a. planeincluding the axis of the runner, the inner and outer longitudinal edgesof the same blade sloping 4 I away in the same direction whetherforwardly or rearwardly from an'imaginary plane which includes the axis;in the construction shown in Fig. 8 the outer and in ner longitudinaledges a and b respectively slope forwardly in the direction of rotation,while in the construction shown in Fig. 9 the outer and innerlongitudinal edges a and b slope rearwardly.

Having thus described my invention, What I claim and desire-to secure byLetters Patent of the United States is l. A fan runner comprising aplurality of scooped blades the outer and inner longitudinal edges ofwhich lie on substantially conical surfaces differently inclined to theaxis of the runner, the outer cone being less inclined than the innercone, and both cones being truncated, and each blade being so set thatboth its outer and inner longitudinal edges deviate from a planerotating on the axis of the fan runner; means joining the inner ends ofthe blades, and means joining the outer ends of the blades.

2, A fan runner comprising a plurality of blades the outer and innerlongitudinal edges of which lie on substantially conical surfacesdifferently inclined to the axis of the runner, the outer cone beingless inclined than the inner cone, and both cones being truncated, andeach blade being so set that both its outer and inner longitudinal edgesdeviate from a plane rotating on the axis of the fan runner; and meansjoining the ends of the blades.

3. A fan runner comprising a plurality of scooped blades the outer andinner longitudinal edges of which lie on substantially conical surfacesdifiierently inclined to the axis of the runner, the outer cone beingless inclined than the inner cone, and both cones being truncated, andeach blade being so set that both its outer and inner longitudinal edgesdeviate from a plane rotating on the axis of the fan runner.

i. A fan runner comprising a plurality o tapered and scooped blades, theouter and inner longitudinal edges 01 which lie on substantially conicalsurfaces diil'erently inclined to the axis of the runner, the outer conebeing less inclined than the inner cone, and both cones being truncated,and each blade being so set that both its outer and inner longitudinaledges deviate from a plane rotating on the axis of the fan runner; adisk joining the inner edges of said blades, and a ring joining theouter edges of said blades.

In testimony whereof I have signed my name to this specificati n in thepresence of two subscribing witnesses.

JAMES KEITH.

Witnesses WALLACE FAIRWEA'IIIER, J 01m MGCLEARY, Jr.

